The intent of this program-project grant is to investigate the epidemiology of breast cancer and benign breast disease. The work will include: the determination of epidemiologic characteristics of women diagnosed as having different histologically-defined breast conditions; epidemiological and laboratory studies of the secretion of mutagenic substances into breast fluids, including their chemical characterization and potential DNA-damaging and repair activity on cells in human breast fluids and their metabolic activation, and epidemiologic investigations of estrogen-binding beta-globulin in blood and breast fluids.